This invention relates to ink tanks.
This invention is directed to an ink tank for use in a printing device which has a plurality of ink chambers including one ink chamber having a supply/delivery port and a porous element in the chamber for absorbing and holding ink, and one or more free ink chambers, i.e., chambers which contain only ink and are free of ink absorbing and holding elements. When an ink tank is filled with ink, the ink displaces the air in the tank. However, if all of the air in the tank is not displaced by ink, the air remaining in the tank forms one or more air bubbles in the tank. Since air is lighter than ink, the air bubble or bubbles remaining in the tank rise and often rise to the top of the tank. Since ink tanks typically contain a number of ink chambers, with ceilings of the same height, one or more air bubbles tend to form at the top of each chamber. When the ink tank is heated, which may happen in normal operation of the device in which it is located, or the ambient atmospheric pressure in which the ink tank is located is low, such as may occur at high altitudes, the air bubble or bubbles trapped in one or more ink chambers of an ink tank will expand, pushing ink into the ink tank chamber which contains a wick or foam and an ink tank supply/delivery port, which is sealed prior to use. When an ink tank port seal is removed, however, ink may be forced out through the supply/delivery port because of the force exerted on the ink by expanded trapped air bubble(s). The invention is directed to providing free ink tank chambers with ceilings which are lower than the ceiling height of the ink tank chamber which contains an ink absorbing and holding element and the ink supply/delivery port. With this ink tank construction, any air trapped inside of the ink tank when the ink tank is filled will tend to rise to the highest level in the ink tank, which will be the top portion of the ink tank supply/delivery port chamber with a ceiling that is higher than the ceiling of any of the free ink tank chambers. Moreover, since no air will be trapped in the free ink tank chambers, and air will only become trapped in one ink tank chamber which contains the ink absorbing holding element, less air will be trapped in the tank as a whole. This means that the amount of air trapped in the ink tank will be less than if air were trapped in a number of ink chambers. As a result, if the ink tank is heated or placed in a relatively low pressure atmosphere, there will be less air to expand, and less of a force exerted on the ink by the expanded air, resulting in less chance of leakage from the ink tank due to expansion of air trapped in the ink tank during the ink filling process.
This invention reduces the amount of trapped air in an ink tank containing one or more free ink chambers and an ink delivery port chamber when the ink tank is filled with ink by lowering the height of the ceiling of each free ink chamber relative to the height of the ceiling of the ink delivery port chamber and further by filling the ink tank with ink.